Rail tickets do I need to validate before boarding

No, no need to do that in Germany.

No, if you travel Deutsche Bahn long-distance and also all on ticket included regional trains in combination with it.

But on some regional trains and S-Bahnen (depending on the city) you have to stamp a single trip or a day ticket (paper version) before starting the journey, e. g. Berlin day ticket. A time stamp machine stands near the ticket machine (example).

Have a good journey.

I see that I can purchase a Bavaria day ticket for my wife and self for 29 euros (Munich airport to Augsburg), but can only ride on regional trains, not the ICEs.

That would limit me to wait for over an hour and a half waiting for a regional train.

That's correct. You also have to wait till after 9 am to ride one of the trains. But they are good from 9:00 am to 3:00 am the following day. Or on weekends and holidays, it is from midnight to 3 am the following day.

There are Sbahns from the Munich Airport to the Munich Train Station (München HBF) about every 20 minutes. There are RE or RB trains from the München HBF to Augsburg about every thirty minutes. We just rode this route in April.

You can ride all these with a Bayern Ticket (39 Euros).

https://int.bahn.de/en/offers

Are you going to land and clear passport control and collect you luggage before 9 AM as mentioned above?

Gary,
Thanks for the help.

I rechecked the scheduled trains from Munich HBH to Augsburg (July 12) and found regional trains after 0930 hours:

0958 to Augsburg

then several ICE trains

then another regional EC at
1148
then another regional RB at
1158
not another regional until
1402

Change the "Mode of Transportation" to "Local Transportation Only"

There a RE or RB trains at
9:35
9:58
10:35
10:57
etc.

Gary,
Many thanks, now I will likely do the Bavaria ticket for us.

Most rail tickets in German come out of the machine with the date and time of purchase printed on them, and they are valid for that day, or maybe the next, or, in the case of in-town transit, for so many hours. These tickets are too wide to fit in the cancelling machines in a station.

A few tickets, U-Bahn, trams, and buses can be purchased in advance to be used at an indefinite time in the future and have to be time stamped in a machine when used. These tickets have "Hier entwertet" printed on one end with arrows (triangles, actually) on the end that has to be inserted when validated (time stamped).

I presume that if we purchase a Bavaria ticket for the day that we don't have to validate it on the S Bahn.

"No. You do not need to validate the tickets.
Bayern-Tickets from the ticket machines at S-Bahn/U-Bahn stations, via MVG customer centers and sales outlets and the ticket printers on regional bus services are validated as soon as they are purchased"

Translated with DeepL from German MVV Bayern-Ticket page, faq #4 "Muss ich stempeln?" (Do I have to stamp?).

That would limit me to wait for over an hour and a half waiting for a
regional train.

Only if you have to wait from 7:30. The rest of the time there are about 2 regional train an hour from Munich to Augsburg. So you wait an average of 15 minutes.

Hint: If you leave the schedule webpage set for "all" trains, it only shows some of the regional trains, those that will arrive sooner than the fast trains. As Gary says, set the search for "local transportation only".